Bituminous products are widely used in the construction field, and constitute one of the major commodity products in building and road construction. These materials are derived from the residue remaining after crude oil is refined to remove various distillates. Over the past twenty years, there have been many innovations in bituminous materials used in roofing and paving. The principle objectives of these developments are to increase strength and durability, ductility, reduce “creep”, cracking, and surface wear. A typical asphalt shingled roof requires replacement after 12-18 years, and road damage to asphalt may be detected within even the first year of paving. New compositions have substantially extended the lifespan of these materials
Many of the new asphalt materials contain synthetic polymers to create chemical links (both covalent and non-covalent interactions) between the long chain hydrocarbons, thus providing molecular strength. U.S. Pat. No. 5,556,900 discloses a thermoplastic polymer-linked asphalt in which the asphalt is reacted with an epoxide polymer resulting in a composition with low gelation, high emulsion forming capacity, and improved rheology. Heat treatment at 135 degrees C., results in covalent bonding between the polymer and the asphalt. In other polymer-containing bitumens, there is typically non-covalent adhesion binding of components.
For example, U.S. Pat. No. 5,473,000 teaches a method for improving bitumen by adding to asphalt a thermoplast or thermoelastomer, and a wood resin, resulting in enhanced binding properties. A linear polyethylene modified asphaltic composition is disclosed in U.S. Pat. No. 4,868,233, which has improved storage stability and creep resistance. Another polymer additive approach is disclosed in U.S. Pat. No. 5,322,867 for a bituminous mixture containing a polymer comprising one block of a conjugated diolefin methacrylate and a block of a functionalized acrylic monomer, giving improved properties over neat asphalt.
Some of the most significant developments in asphalt and tar composition involve various strategies for combining the strength and resiliency of latex polymers with bituminous materials. U.S. Pat. Nos. 4,485,201 and 5,436,285 disclose incorporation of finely divided rubber into asphalt compositions. In a variation, U.S. Pat. No. 5,811,477 utilizes reclaimed rubber particles, latex rubber, preferably styrene butadiene, and an aqueous asphalt emulsion to achieve low temperature processing, thereby reducing environmental contamination from latex volatiles.
U.S. Pat. Nos. 5,451,621 and 5,973,037 teach the infusion of particular latex polymers characterized as styrene-ethylene-butylene-styrene block copolymers into bituminous products, including asphalt, to raise the softening point of the blend and increase resistance to ultraviolet radiation, ozone, and fatigue. In yet another application of rubber in the asphalt art, U.S. Pat. No. 5,704,971 discloses the pretreatment of crumb rubber with peroxide, adding the treated rubber to asphalt in the presence of a compatibilized binder to produce an asphalt having improved settling properties of the binder, and reduced tendency to ravel.
While the objectives of improved durability, ductility, strength, and other related performance improvements, modification of bituminous substances has brought about new problems. The same molecular interactions which achieve enhanced stability and binding efficiency of the asphalt components, especially in the class of latex polymer blends known as SuperPave, also render the material extremely difficult to remove from paving equipment such as asphalt distributors and oilers, spreaders and the like, roofing manufacturing equipment and applications equipment. The buildup of these materials on equipment, particularly painted and bare metallic surfaces, leads to uneven dispensing, plugged nozzles, and impaired release of asphalt from distributors and spreaders. In many instances uneven distribution of asphalt in pavement requires repaving at substantial cost to the industry.
Classically, equipment has been cleaned by the use of common petroleum distillates such as kerosene, diesel fuel, or more purified fractions, and wood resin compounds such as turpentine. Usually cleaning with these substances requires mechanical intervention as by brushing, rubbing with cloth or abrasives Use of such conventional substances has led to environmental contamination and exposure of cleanup personnel to toxic, and even carcinogenic substances. Moreover, the extreme intractability of the advanced polymer blended bitumens to conventional cleaning solvents increases the volumes needed to soften and remove them from machinery surfaces. Incomplete removal of the asphalt results from the difficulty of conventional solvents to penetrate the asphalt matrix. This increases costs of cleanup to the industry, in terms of time and materials, and machine efficiency.
Much attention has been given to development of asphalt release agents that preventing sticking of bituminous materials to machinery. U.S. Pat. No. 5,900,048 discloses a release composition combining lethicin with a dispersing agent such as propylene glycol ethers or ether acetates. Other release agents have been proposed such as a combination of polycycloaliphatic amines and polyalkylene glycols (U.S. Pat. No. 5,961,730), cleaning by hydrogen peroxide together with iron catalysts (U.S. Pat. No. 5,725,687), fatty acids, in combination with preferably an anionic surfactant (U.S. Pat. No. 5,494,502, and a water based solution of magnesium chloride, a phosphate ester, an anionic alcohol surfactant (U.S. Pat. No. 5,322,554).
All of the foregoing release technologies have as a common strategy, forming a slippery barrier coating on a metal surface to prevent adhesion of asphalt, thus allowing it to slide readily from the treated surface. None of these compounds can be expected to appreciably penetrate the asphalt itself, except as a softener at the immediate undersurface. Thus, effective removal of asphalt already set on machinery is not addressed. A need exists for an effective asphalt removal agent, especially for modern bituminous polymer-containing formulations.